The present invention relates to ram air turbines, and more particularly to ram air turbines having generators and methods for testing the same.
Deployable ram air turbines (RATs) are used on aircraft to provide an emergency power supply to power a generator, hydraulic pump, etc. When not in use, the RAT is generally stowed within the aircraft fuselage. When the aircraft is in flight, the RAT can be deployed to generate power as turbine blades of the RAT spin in oncoming airflow around the aircraft. The RAT can be deployed as a secondary or emergency system when power is unavailable from primary systems of the aircraft.
RATs must be periodically tested to ensure proper operation, particularly because RAT usage is generally infrequent. Conventional RATs use brushless wound-field synchronous generators to generate electrical power. With such wound-field generators, the RAT must be deployed to enable the generator to be rotated to perform testing. Testing is not possible when the RAT and its wound-field generator are stowed and at rest. Although it is particularly desirable to test components of the generator's rotor, wiring (i.e., windings) of the rotor of the wound-field generator are not accessible to an operator when the RAT is stowed and non-operational. In addition, wound field synchronous machines are very complex, typically with three electrical stages (main, exciter and PMG) and rotating rectifiers, with increased needs for reliability inspections.